In Agreement and Head Movement, Ian Roberts explores the consequences of Chomsky's
conjecture that head-movement is not part of the narrow syntax, the computational system that
relates the lexicon to the interfaces. Unlike other treatments of the subject that discard the
concept entirely, Roberts's monograph retains the core intuition behind head-movement and examines
to what extent it can be reformulated and rethought. Roberts argues that the current conception of
syntax must accommodate a species of head-movement, although this operation differs somewhat in
technical detail and in empirical coverage from earlier understandings of it. He proposes that
head-movement is part of the narrow syntax and that it applies where the goal of an Agree relation
is defective, in a sense that he defines. Roberts argues that the theoretical status of
head-movement is very similar--in fact identical in various ways--to that of XP-movement. Thus
head-movement, like XP-movement, should be regarded as part of narrow syntax exactly to the extent
that XP-movement should be. If one aspect of minimalist theorizing is to eliminate unnecessary
distinctions, then Roberts's argument can be seen as eliminating the distinction between
""heads"" and ""phrases"" in relation to internal merge (and therefore reducing the
distinctions currently made between internal and external merge).